107 
other, which are deposited round the mouths of room xi. 
the tubes at regular periods. The animal, 
and the coral itself, when fresh, are bright 
green, but the coral soon becomes red when 
exposed to the air. 
The remainder of these animals form and live 
in a fleshy or calcareous bark, which is often 
supported by a fibrous chalky or bony axis. 
They constitute three families, dependent on 
the nature of the axis. 
The first of these families is the Ceratophytes 
( 'Corallidce ), so called from the horny and tree¬ 
like nature of their axes, and are distinguished by 
the axis being branchy and solid, and attached 
to marine bodies by its expanded base. 
The genera of this family are distinguished »* 
by the structure of the axis, and the form and 
permanence of the bark. In the common Red 
Coral (' Cor allium ) the axis is continued, solid, 
and calcareous, and generally of a bright red 
colour, though it is sometimes found white. 
In Isis and Melitea the axis is equally calca¬ 
reous, but jointed, and in the first the inter¬ 
nodes, or parts between the joints, are solid, and 
the joints cartilaginous, whilst in the latter the 
internodes are fibrous, and the knots are spongy 
and swoln. The knots at the base of the axis of 
these genera, and especially of the Horse-tail 
Coral, become obliterated in old age, when they 
are 
